U.S. patent number 7,486,234 [Application Number 10/547,042] was granted by the patent office on 2009-02-03 for microwave connector, antenna and method of manufacture of same.
This patent grant is currently assigned to QinetiQ Limited. Invention is credited to James Paul Watts.
United States Patent |
7,486,234 |
Watts |
February 3, 2009 |
Microwave connector, antenna and method of manufacture of same
Abstract
A connector adapted to transfer microwave energy between two
planes within 45.degree. of perpendicular to one another,
comprising a first member comprising a first conductor separated
from a first conductive ground plane separated by a first
dielectric, the first dielectric having a slot formed therein; and
a second member comprising a second conductor separated from a
second ground plane by a second dielectric, the second conductor
being provided with an electrical connection to the second ground
plane at a first end of the second member; in which the first end
of the second member extends through the slot in the first member
such that the electrical connection is positioned between first
ground plane and first conductor. The connector may be a microwave
antenna, in which case the first conductor forms a microstrip patch
antenna. A method of producing such connectors and an array of such
antennas is also disclosed.
Inventors: |
Watts; James Paul (Bodmin,
GB) |
Assignee: |
QinetiQ Limited
(GB)
|
Family
ID: |
9954195 |
Appl.
No.: |
10/547,042 |
Filed: |
February 27, 2004 |
PCT
Filed: |
February 27, 2004 |
PCT No.: |
PCT/GB2004/000792 |
371(c)(1),(2),(4) Date: |
August 26, 2005 |
PCT
Pub. No.: |
WO2004/079863 |
PCT
Pub. Date: |
September 16, 2004 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20060170593 A1 |
Aug 3, 2006 |
|
Foreign Application Priority Data
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|
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Mar 6, 2003 [GB] |
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0305081.2 |
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Current U.S.
Class: |
343/700MS;
343/906 |
Current CPC
Class: |
H01Q
9/0407 (20130101); H01Q 9/045 (20130101); H01R
12/58 (20130101); H01R 11/01 (20130101); H01R
2201/02 (20130101); H01R 12/523 (20130101) |
Current International
Class: |
H01Q
1/38 (20060101) |
Field of
Search: |
;343/700MS,906 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0 283 396 |
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Sep 1988 |
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EP |
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1 420 207 |
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Jan 1976 |
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GB |
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2 128 416 |
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Apr 1984 |
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GB |
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2 219 438 |
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Dec 1989 |
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GB |
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2 229 582 |
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Sep 1990 |
|
GB |
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WO 02/33782 |
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Apr 2002 |
|
WO |
|
Other References
Hambaba, et al. "Intelligent Hybrid System for Data Mining",
Proceedings of the IEEE, pp. 111 (1996). cited by other.
|
Primary Examiner: Dinh; Trinh V
Assistant Examiner: Duong; Dieu Hien T
Attorney, Agent or Firm: McDonnell Boehnen Hulbert &
Berghoff LLP
Claims
The invention claimed is:
1. A connector adapted to transfer microwave energy between two
planes having an angle there-between within a range 45.degree. to
90.degree., comprising: a first member comprising a first conductor
separated from a first conductive ground plane by a first
dielectric, the first conductive ground plane and the first
dielectric having a slot formed therein; and a second member
comprising a second conductor separated from a second conductive
ground plane by a second dielectric, the second conductor being
provided with an electrical connection to the second conductive
ground plane at a first end of the second member; in which the
first end of the second member extends through the slot in the
first conductive ground plane such that the electrical connection
is positioned between the first conductive ground plane and the
first conductor with the first and second conductors having an
angle there-between within the range 45.degree. to 90.degree.;
wherein the electrical connection is selected from the group of
electrical connections consisting of at least one conductive via
which connects the second conductor and the second conductive
ground plane through the second dielectric and the second conductor
and the second conductive ground plane that extend around an end of
the second dielectric to contact one another.
2. The connector of claim 1 in which one or more of the first and
second members is generally planar.
3. The connector of claim 2 in which the first and second
conductors are perpendicular to one another.
4. The connector of claim 1 in which the electrical connection is
positioned approximately a quarter of the wavelength in the second
dielectric at or about which the connector is to be used from the
first conductive ground plane.
5. The connector of claim 1 in which the first member is provided
with a further, third, conductive ground plane spaced from the
first ground plane by a third dielectric.
6. The connector of claim 1 in which one or more of the dielectrics
comprises dielectric foam, solid dielectric or an air gap.
7. The connector of claim 6 in which one or more of the dielectrics
comprise a layer of dielectric foam and a layer of solid
dielectric.
8. The connector of claim 6 in which one or more of the dielectrics
comprise a sheet of solid dielectric separated from an adjacent
conductor or an adjacent conductive ground plane by an air gap.
9. The connector of claim 1 in which a support dielectric is
provided on the opposite side of the first conductor to the first
dielectric.
10. The connector of claim 1 in which the second conductor
comprises a planar element which is tapered such that it reduces in
width as it extends away from the first end of the second
dielectric.
11. An antenna comprising: an antenna structure comprising an
antenna patch and a first conductive ground plane separated by a
first dielectric; a feed structure comprising a feed conductor and
a second conductive ground plane separated by a second dielectric;
the feed conductor and the second conductive ground plane being
provided with an electrical connection therebetween at a first end
of the feed structure; in which the feed structure extends through
a slot in the first conductive ground plane and the first
dielectric at an angle within a range 45.degree. to 90.degree. to
the antenna structure such that the electrical connection lies
between the first conductive ground plane and the antenna patch;
wherein the electrical connection is selected from the group of
electrical connections consisting of at least one conductive via
which connects the second conductor and the second conductive
ground plane through the second dielectric and the second conductor
and the second conductive ground plane that extend around an end of
the second dielectric to contact one another.
12. The antenna patch of claim 11 in which the feed structure and
the antenna structure are perpendicular to one another.
13. The antenna of claim 11 in which the electrical connection is
positioned approximately a quarter of the wavelength in the second
dielectric at or about which the antenna is to be used from the
first conductive ground plane.
14. The antenna of claim 11 in which the antenna structure is
provided with a further, third conductive ground plane spaced from
the first ground plane by a third dielectric.
15. The antenna of claim 11 in which the feed conductor is tapered
such that it reduces in width as it extends away from the first end
of the second dielectric.
16. The antenna of claim 11 in which the antenna is adapted to
operate in the microwave spectrum, between 2 GHz and 18 GHz.
17. A method of manufacture of a connector adapted to transfer
microwave energy between two planes, comprising: a) forming a first
laminar structure comprising a first conductor and a first
conductive ground plane separated by a first layer of dielectric;
b) forming a second laminar structure comprising a second conductor
and a second conductive ground plane separated by a second layer of
dielectric; c) passing at least one electrical conductive via
through the second laminar structure at a first end thereof to
connect second conductor and second conductive ground plane; d)
forming a slot in the first laminar structure through the first
conductive ground plane and the first dielectric; and e) fixing the
second laminar structure in the slot such that the electrical
conductive via or vias are between the first conductive ground
plane and the first conductor.
18. The method of claim 17 in which the connector acts as an
antenna and the first conductor is a microstrip antenna.
19. The method of claim 17 in which the step of forming the first
or second laminar structure includes the steps of forming one or
both sides of a solid dielectric sheet with one or more conductive
layers, masking at least one area of one or each conductive layer,
etching any unmasked areas to form the first or second conductors
or the first or second conductive ground planes and then fixing the
solid dielectric to a layer of foam dielectric.
20. The method of claim 17 in which the step of fixing the second
laminar structure in the slot includes the step of positioning the
electrical via or vias a distance of a quarter of a wavelength, in
the second dielectric layer and at which the connector is to be
used, from the first conductive ground plane.
21. The method of claim 17 in which the first laminar structure
includes a further, third conductive ground plane separated from
the first ground plane by a third layer of dielectric and the step
of forming a slot in the first laminar member includes forming the
slot through the third ground plane and third dielectric layer.
22. The method of claim 17 in which the second laminar structure is
fixed perpendicular to the first laminar structure.
Description
This application is a 371 of PCT/GB04/00792 Feb. 27, 2004.
This invention relates to microwave connectors and antennas
typically for use in the microwave spectrum. It also relates to
methods of manufacture of same and arrays of such antennas.
Microstrip patch antennas are attractive candidates for the
radiating elements of a phased array on account of their low cost,
compactness and inherent low mutual coupling. These antennas
consist of a rectangular or circular metal patch on a dielectric
substrate, backed by a continuous metal ground plane. They are
conventionally fed microwave energy by either a probe feed, in
which a coaxial connector or cable feeds the patch from behind the
ground plane; by a microstrip feedline, in which a microstrip
transmission line is connected directly to the patch in the plane
of the patch; or through an aperture-coupled feed, in which a
microstrip line parallel to the plane of the patch on the opposite
side of the ground plane to the patch excites the patch through a
slot in the ground plane adjacent to the patch.
However, all of these methods have inherent disadvantages. When
microstrip patch antennas are used as the radiating elements in a
phased array, a perpendicular feed may be desirable--that is, a
feed which extends perpendicularly to the patch. This allows space
for active components such as amplifiers or phase shifters to be
placed behind the antenna ground plane on a single, perpendicular
circuit board. Accordingly, it is preferred not to use the
microstrip feedline or aperture-coupled feeds described above. As
regards the probe-fed method or other perpendicularly-fed methods
that have been suggested, these methods prove impractical for a
large array as they require access behind the array face for
soldering or tightening electrical connections. Previous
perpendicular feeds have also introduced an undesirable asymmetry
into the antenna radiation pattern.
The invention provides, according to a first aspect of the
invention, a connector adapted to transfer microwave energy between
two planes within 45.degree. of perpendicular to one another
comprising: a first member comprising a first conductor separated
from a first conductive ground plane by a first dielectric, the
first conductive ground plane having a slot formed therein; and a
second member comprising a second conductor separated from a second
conductive ground plane by a second dielectric, the second
conductor being provided with an electrical connection to the
second conductive ground plane at a first end of the second member;
in which the first end of the second member extends through the
slot in the first conductive ground plane such that the electrical
connection is positioned between first conductive ground plane and
the first conductor, with the first and second conductors within
45.degree. of perpendicular.
This provides a possibly symmetric connector which allows transfer
of microwave energy between two planes which reduces the problem of
non-uniformity of radiation whilst being easily manufactured and
requiring no soldered joints or similar. In a preferred embodiment
the two planes and the first and second conductors are
perpendicular to one another.
One or more of the first and second members may be generally
planar. In a preferred embodiment both first and second members are
generally planar, or at least that portion of the second member
that extends through the slot in the first conductive ground
plane.
In a preferred embodiment the connector forms an antenna, where the
first conductor is a microstrip patch antenna. This advantageously
provides a perpendicularly fed antenna with a reduced
non-uniformity of radiation and which is easily assembled.
The first member may be provided with a further, third, conductive
ground plane spaced from the first ground plane by a third
dielectric. This has been shown to improve the performance of the
connector. Further conductive ground planes may be provided in a
similar fashion.
One or more of the dielectrics may comprise dielectric foam, solid
dielectric or an air gap. In a preferred embodiment one or more of
the dielectrics comprise a layer of dielectric foam and a layer of
solid dielectric. This allows the conductors and conductive ground
planes to be directly deposited on the solid dielectric. In an
alternative embodiment one or more of the dielectrics may comprise
a sheet of solid dielectric separated from the adjacent conductor
or conductive ground plane by an air gap. Separation of the
conductors and conductive ground plane may be preserved by use of
spacers.
A support dielectric may be provided on the opposite side of the
first conductor to the first dielectric. The support dielectric may
be a solid dielectric. This allows the first conductor to be
directly deposited on the support dielectric when it is
impracticable to be supported by the first dielectric, for example
if the surface of the first dielectric adjacent to the first
conductor is a foam dielectric.
The second conductor may comprise a planar element which may be
tapered such that it reduces in width as it extends away from the
first end of the second dielectric. The taper may be continuous or
may be formed of one or more discrete steps.
In a preferred embodiment, the second conductor comprises several
steps in order to match the antenna to a microstrip line with
50.OMEGA. impedance.
In a preferred embodiment, the electrical connection comprises at
least one electrical via which connects the second conductor and
second conductive ground planes through the second dielectric.
There may be three electrical vias. Alternatively, the second
conductor and second conductive plane may extend around the first
end of the second dielectric ground sheet to contact one
another.
The connector may be adapted to operate in the microwave spectrum,
typically between 2 GHz and 18 GHz. In a preferred embodiment it is
adapted to operate at around 10 GHz. In a preferred embodiment, the
electrical connection may be positioned approximately a quarter of
the wavelength in the second dielectric at or about which the
connector is to be used from the first, or if present third,
conductive ground plane.
According to a second aspect of the invention, there is provided an
antenna comprising: an antenna structure comprising a microstrip
patch antenna and a first conductive ground plane separated by a
first dielectric; a feed structure comprising a feed conductor and
a second conductive ground plane separated by a second dielectric;
the feed conductor and the second conductive ground plane being
provided with an electrical connection therebetween at a first end
of the feed structure; in which the feed structure extends through
a slot in the first conductive ground plane within 45.degree. to
perpendicular to the antenna structure such that the electrical
connection lies between the first conductive ground plane and the
antenna patch.
This provides a convenient possibly perpendicularly fed antenna
which suffers less from non-uniform radiation than prior art
antennas, and is easily assembled as it is not necessary to make
connection directly behind the antenna face as with the prior art.
In a preferred embodiment the feed structure extends perpendicular
to the antenna structure.
The antenna is typically suitable for both transmission and
reception. When receiving, microwave energy incident on the antenna
patch excites an electromagnetic field in the slot in the first
conductive ground plane. This induces an electromagnetic field
between the feed conductor and the second conductive ground plane
and hence transfers the microwave energy to the feed conductor
where it can be passed to conventional detection apparatus.
Similarly, for transmission, microwave energy is passed to the feed
conductor which causes a varying electromagnetic field to be set up
between the feed conductor and the second conductive ground plane.
This in turn induces an electromagnetic field in the slot in the
first conductive ground plane and excites the patch antenna, which
radiates the microwave energy in the usual fashion.
The antenna structure may be provided with a further, third
conductive ground plane spaced from the first ground plane by a
third dielectric. This has been shown to improve the performance of
the antenna. Further conductive ground planes may be provided in a
similar manner.
One or more of the dielectrics may comprise dielectric foam, solid
dielectric or an air gap. In a preferred embodiment one or more of
the dielectrics comprise a layer of dielectric foam and a layer of
solid dielectric. This allows the conductors and conductive ground
planes to be directly deposited on the solid dielectric. In an
alternative embodiment one or more of the dielectrics may comprise
a sheet of solid dielectric separated from the adjacent conductor
or conductive ground plane by an air gap.
Separation of the conductors and conductive ground planes may be
preserved by use of spacers.
A support dielectric may be provided on the opposite side of the
antenna patch to the first dielectric. The support dielectric may
be a solid dielectric. This allows the antenna patch to be directly
deposited on the support dielectric when it is impractical to be
supported by the first dielectric, for example if the surface of
the first dielectric adjacent to the antenna patch is a foam
dielectric.
The feed conductor may be tapered such that it reduces in width as
it extends away from the first end of the second dielectric. The
taper may be continuous or may be formed of one or more discrete
steps.
In a preferred embodiment, the second conductor comprises several
steps in order to match the antenna to a microstrip line with
50.OMEGA. impedance.
In a preferred embodiment, the electrical connection comprises at
least one electrical via which connects the feed conductor and
second conductive ground plane through the second dielectric. There
may be three electrical vias. Alternatively, the feed conductor and
second conductive ground planes may extend around the first end of
the second dielectric to contact one another.
The antenna may be adapted to operate in the microwave spectrum,
typically between 2 GHz and 18 GHz. In a preferred embodiment it is
adapted to operate at around 10 GHz. The electrical connection may
be positioned approximately a quarter of the wavelength in the
second dielectric at or about which the antenna is to be used from
the first, or if present, the third conductive ground plane.
According to a third aspect of the invention, there is provided a
method of manufacture of a connector adapted to transfer microwave
energy between two planes, comprising: a) forming a first laminar
structure comprising a first conductor and a first conductive
ground plane separated by a first layer of dielectric; b) forming a
second laminar structure comprising a second conductor and a second
conductive ground plane separated by a second layer of dielectric;
c) passing at least one electrical via through the second laminar
structure at a first end thereof to connect second conductor and
second conductive ground plane; d) forming a slot in the first
laminar structure through the first conductive ground plane and the
first dielectric; and e) fixing the second laminar structure in the
slot such that the electrical via or vias are between the first
conductive ground plane and the first conductor.
This method is a great simplification over the prior art in that it
is unnecessary to make soldered joints or cable connections in the
small space available behind a connector face. Typically, the
connector acts as an antenna and the first conductor is an antenna
patch.
In a preferred embodiment the step of forming the first or second
laminar structure includes the steps of forming one or both sides
of a solid dielectric sheet with one or more conductive layers,
masking at least one area of one or each conductive layer, etching
any unmasked areas to form the first or second conductors or the
first or second conductive ground plane and then fixing the solid
dielectric to a layer of foam dielectric.
The first laminar structure may include a further, third conductive
ground plane separated from the first ground plane by a third layer
of dielectric. In such a case, the step of forming a slot in the
first laminar member includes forming the slot through the third
ground plane and third dielectric layer.
The step of fixing the second laminar structure in the slot may
include the step of positioning the electrical via or vias a
distance of a quarter of a wavelength, in the second dielectric
layer and at which the connector is to be used, from the first or,
if present, the third conductive ground plane.
The second laminar structure may be fixed perpendicular to the
first laminar structure.
According to a fourth aspect of the invention, there is provided a
method of transferring microwave energy from one plane to another,
comprising transmitting the energy through a length of parallel
plate waveguide having a short-circuit at an end thereof in which
the short is positioned in a gap between a conductor in the plane
to which the energy is to be transferred and a conductive ground
plane parallel to that conductor, or passing the microwave energy
through the reverse of the above route.
The parallel-plate waveguide and the conductor may be perpendicular
to one another.
In a preferred embodiment, the short-circuit is in a gap between a
conductor in the plane to which the energy is to be transferred and
two parallel conductive ground planes.
The conductor may be an antenna patch adapted to transmit and
receive the microwave energy to be transferred.
According to a fifth aspect of the invention, there is provided an
array of antennas according to the first or second aspects of the
invention. In a preferred embodiment they form a phased array.
There now follows, by way of example, an embodiment of the
invention, described with reference to the accompanying drawings,
in which:
FIG. 1 shows an antenna according to the present invention, showing
the internal structure;
FIG. 2 shows an exploded cross section through line II of FIG. 1;
and
FIG. 3 shows an exploded cross section through line II of FIG. 1
where conductor 41 and conductive ground plane 46 may extend around
the first end 54 of dielectric layer 40 to contact one another.
The antenna 10 shown in the accompanying drawings comprises two
members, a first member or antenna structure 12 and a second member
or feed structure 14. Each of the structures comprise a number of
layers as described below.
The antenna structure 12 comprises two dielectric layers 20, 26
each with a conductive ground plane 24, 28 on its underside. The
first dielectric layer 20 is mounted on top of the second
dielectric layer 26. Each of the dielectric layers comprise an
upper layer of dielectric foam 20a, 26a with a layer of solid
dielectric 20b, 26b attached to the underside. On top of the first
dielectric layer is mounted an antenna support dielectric 30. This
comprises a thin layer of solid dielectric on the underside of
which has been formed a circular antenna patch 22.
The feed structure 14 comprises a single layer of solid dielectric
40. On the rear side of this a conductive ground plane 46 is
provided. On the front of the dielectric layer 40 a conductor 41 is
provided which is shaped so as to define together with the ground
plane an area of parallel-plate waveguide 42 at a first end of the
dielectric layer and a microstrip feed 52 at a second end of the
dielectric layer. The conductor 41 also defines the transition 50
between the two areas 42, 52 by varying width from nearly a half of
the wavelength at which the antenna is to be used in the parallel
plate waveguide region 42 to typical microstrip dimensions (of the
order of a few millimeters) in the microstrip feed region 52. The
transition 50 comprises a number of discrete changes in width of
conductor.
The conductive ground plane 46 and conductor 41 of the feed
structure 14 are electrically connected at the first end of the
dielectric layer by means of a number, in this case three, of
conductive vias 48 which pass through the dielectric layer 40 to
connect the two conductors 41, 46.
The antenna structure is further provided with a slot 32 extending
perpendicularly from but not through the antenna patch 22 through
first and second dielectric layers 20, 26 and ground planes 24,
28.
The first end of the feed structure 14 is fixed inside the slot 32
such that the feed structure 14 lies perpendicular to the antenna
structure 12. The slot is sized so as to fit the feed structure 14
in this position. The feed structure is placed so that the distance
from the conductive vias 48 to the second, outer ground plane 28 of
the antenna structure 12 is approximately a quarter of the
wavelength at which the antenna is intended to be used.
In use as a transmit antenna 10, the signal to be transmitted is
fed to the microstrip region 52 of conductor 41. All ground planes
are held at an earth potential. Conductive vias 48 therefore
provide a short circuit between feed and ground. As the feed
structure 14 is symmetric in the parallel-plate waveguide region 40
about a plane parallel to and centred between conductor 41 and feed
ground plane 46, a symmetric electro-magnetic field is generated in
the region of the slot 32. This induces electromagnetic fields in
the slot 32, which in turn excites the antenna patch 22 which then
transmits in the usual manner.
Reception by the antenna 10 occurs in a similar fashion. Radiation
incident on antenna patch 22 excites an EM field in the slot 32.
This induces an EM field between the feed conductor 41 and the feed
ground plane 46 in the parallel plate waveguide region 42. This
passes through transition 50 to microstrip region 52 where it can
be detected by standard equipment.
The materials and techniques used in the manufacture of the antenna
10 are all well known in the art. The solid dielectrics 30, 20b,
26b are typically random microfibre glass in a PTFE matrix material
having a dielectric constant of 2.2. The solid dielectric 40 is
typically a ceramic in PTFE matrix material having a dielectric
constant of 10.2. The foam dielectrics are typically a rigid foam
plastic based on polymethacrylimide and have a dielectric constant
of 1.05 at 10 GHz. Typical foam thickness for use at 10 GHz are 1.5
mm. Use of the combination of foam and solid dielectrics allows
flat plates of conductive material, typically copper, to be plated
onto the solid dielectric. This can then be etched to define the
conductive areas to be the desired shapes.
To form the antenna described herein laminar structures
corresponding to the antenna structure 12 and feed structure 14 are
formed. This comprises coating three solid dielectric sheets with a
layer of metal, typically copper on one side thereof and a fourth
dielectric sheet with similar layers of metal on both sides. Areas
of these sheets are masked then etched to define the antenna patch
22 on antenna support dielectric 30, first 24 and second 28 ground
planes on solid dielectrics 20b and 26b and conductor 41 and ground
plane 46 of feed structure 14. The masks define the shapes of the
conductive areas as described above.
The antenna support dielectric 30 and solid dielectrics 20b and 26b
are then positioned with foam dielectric layers 20a and 26b between
antenna support dielectric 30 and first solid dielectric 20b and
between first solid dielectric layer 20b and second solid
dielectric layer 26b. This complete antenna structure 12 is then
fixed together using adhesive. The slot 32 is milled out so as to
pass through first and second ground planes 24, 28 and first and
second dielectric layers 20 and 26.
The electrical vias 48 are drilled through the first end of feed
structure 14 and plated to electrically connect conductor 41 and
conductive ground plane 46. The feed structure 14 is then fixed in
the slot 32 such that electrical vias are approximately a quarter
of the wavelength at which the antenna (in the feed structure 14
dielectric 40) is to be used from the second ground plane 28.
* * * * *